If you have access to a swimming pool and some weights, it's pretty easy to check buoyancy. I've done it on brand new jackets and found variation of a couple of pounds within same model...! For the rest, check out seams/sewing, especially in stress areas (under arms, across shoulders), and buckles/zippers (brush zips clean and then silicon 'em before storing for winter helps a lot come Spring). Nothing you can do about fading and illegible printing - that's the end, period.
As for ranger checkout, it's the one procedure I've never objected to, anywhere. Do you not want to know if the device that's meant to add flotation in the event your life depends on it has a problem? I do, and don't care who discovers it...